Drilling installation for extracting products from underwater sea beds

ABSTRACT

An installation for extracting products from underwater sea beds comprises a base section which is permanently sunk in the sea bed, a reusable well section, and water-tight flexible connecting means releasably connecting together the base section and well section. The well section has sufficient internal dimensions to allow workmen and equipment to pass therethrough and is open to the atmosphere so that the working space for the workmen is maintained at atmospheric pressure. The reusable well section may be disconnected from the base section and reused again at another extracting site.

United States Patent Desmoulins [54] DRILLBQG INSTALLATION FOREXTRACTING PRODUCTS FROM UNDERWATER SEA BEDS Robert Desmoulins, 3,Avenue de St. Amand, 59 Valenciennes,

France [22] Filed: Dec. 30, 1969 [21] Appl. No.: 889,357

[72] Inventor:

[30] Foreign Application Priority Data Dec. 31, 1968 France ..68l9266[52 us. c1 ..175/6, 175/171 [51] 1m. (:1. ..E2lc 19/00 [58] FieldofSearch ..175/6, 8, 9, 7; 166/5, .6

[56] 7 References Cited UNITED STATES PATENTS 3,344,612 10/1967 Rininger..175/9 x 1,465,664 22/1923 Griesser ..175/9 Oct. 24, 1972 2,171,6729/1939 Plummer ..175/9 X 2,503,516 4/1950 Shrewsbury ..175/8 X 2,622,40412/1952 Rice ..175/8 X 3,202,217 8/1965 Watts et a1 ..175/5 X PrimaryExaminer-Stephen J. Novosad Assistant Examiner-Richard E. FavreauAttorney-Robert E. Burns [5 7] ABSTRACT An installation for extractingproducts from underwater sea beds comprises a base section which ispermanently sunk in the sea bed, a reusable well section, andwater-tight flexible connecting means releasably connecting together thebase section and well section. The well section has sufficient internaldimensions to allow workmen and equipment to pass therethrough and isopen to the atmosphere so that the working space for the workmen ismaintained at atmospheric pressure. The reusable well section may bedisconnected from the base section and reused again at anotherextracting site.

10 Claims, 17 Drawing Figures PATENTEDUEI 24 1972 saw DIOF 13PATENTEDUBI 24 1912 sum 030F1- 13 PATENTEDUCT 24 I972 sum 0 0F 3PATENTEB 0m 24 m2 sum as or 1 PATENTEU 3.700.048

sum UBUF 1s PMENTED 24 I97? 3. 709.048

sum 09 0F 13 Fig/10 Pmmtnnmmm v I -3,700.048

sum 120; 13 A PATENTEDU 24 I972 sum 13m 13 DRILLING INSTALLATION FOREXTRACTING PRODUCTS FROM UNDERWATER SEA BEDS The invention relates to aninstallation for laying underwater bases leading to the open airintended for the extraction of hydrocarbons or any other solid, liquidor gaseous mineral products contained in the underwater bed itself, ortaken from the surface of it. This same apparatus can be used foranchoring points for support pylons, fixed or floating islands and allsurface maritime installations.

For this type of installation, it has heretofore been necessary to findavailable personnel with long training in diving techniques and who werewilling to work very arduous conditions.

The present invention relates to an apparatus for installing such aninstallation and which obviates the forementioned drawbacks.

The present invention is characterized in that the drilling operationfor a shaft opening to the air, the base center-point sleeve of which isimplanted in the sea bed is carried out by rotation of the center-pointitself.

The present invention will be better understood with the aid of thefollowing description, made by way of FIG. 2 is a fragmentary axialsection showing the lower portion of the pivot pipe;

FIG. 3 is an axial sectional view showing on a larger scale the pivot ofthe well drill;

FIG. 4 is a fragmentary vertical section of the well p FIG. 5 is anaxial section showing on a larger scale the pivot and the lower portionof the well pipe;

FIG. 6 is an axial section showing the equipment for installing thefirst driiling tube;

FIG. 7 is a fragmentary axial section showing on a larger scale amodified form of embodiment of the lower portion of the pivot pipe;

FIG. 8 is a fragmentary axial section showing another form of embodimentof the lower portion of the pivot P p FIG. 9 is a diagrammatic sectionalview of an anchoring layer;

FIG. 10 is a plan view from above of a workshop ship;

FIG. 1 1 is a diagrammatic side elevational view from astern of theworkshop ship;

FIG. 12 is a fragmentary plan view from above showing the workshop shipon a larger scale;

FIG. 13 is a plan view from above of a pontoon workshop in its openposition;

"FIG. 13a is a diagrammatic vertical section of the central portion ofthe pontoon of FIG. 13, and

FIG. 14 is a plan view from above of a ship for laying the anchoringmeans.

These internal arrangements are carried out on land before the materialis embarked on the floating workshop and transport to the site where thedrilling is to be carried out.

If the rig does not have a prohibitive length it is possible tocompletely assemble same on the loading wharf and then tow if over thewater to the implantation site.

To put the rig into the vertical position, balancing ballast tanks maybe used.

Each sleeve section of the shaft-rig thus has a definite place in theassembly.

In its entirety, the shaft-rig, shown in the present FIG. 1, isessentially composed of three principal parts, a center-point sleeve 1implanted in the underwater bed, a shaft sleeve 2 which leads to theopen air and one or several hoops 3 which form the articulated jointsand serve as connections between the center point sleeve 1 and the shaftsleeve 2.

The center-point sleeve is intended to be solidly implanted in theunderwater bed.

This implantation must bring about and guarantee that the base of theentire shaft-rig is waterproof.

As a result, a rigid implantation; similar to that of a solidly drivenpile, should be made deep into the underwater bed.

The fact of being thus rigidly implanted then imposes the obligation ofguaranteeing the installation against all possible oscillations aboutthe vertical axis which could be provoked by a shock which might affectthe waterproofing of the sleeve 4 and of the first boring tube 5.

Although underwater beds are generally considered to be calm regions,for the sake of this invention, however, they are considered as alwaysbeing susceptible to perturbations by liquid masses in variousdirections.

In order to eliminate all possibility of incidents due to forcesprovoked by these large volumes of liquid in motion, the head of thesleeve 4 which rigidly extends from the ground, is provided with aflexible unit 6, which allows slight oscillations of the center-pointsleeve about the vertical axis of the shafts.

In certain particular doubtful cases of violent liquid movements, theseoscillations can be corrected and reduced to a minimum by the additionof adjustable stays 7 which may be adjusted from inside the shafts. Inaddition, it should be clarified that according to the geologicalcomposition of the underwater terrain and relief at the implantationsite, the shaft-rig and, particularly, the center-point sleeve 1 may beof a different conception thereby allowing the judicious adaptation tothe site under consideration.

The center-point sleeve 1 essentially consists of a cylindrical bodywith a double wall forming a waterproof space where the water ballast 8is provided and which allows all balancing operations for traction orcompression necessary to the implantation or to the exploitation of theshafts.

This cylindrical body ends at the lower part by a spherical or conicalchamber 9, containing, in part, all materials and special gear intendedfor the work of implanting of this center-point sleeve 1 and the placingof the first tube 5 to carry out the boring.

In order to allow for the installation of all the necessary materialsfor the implantation of the shaft-rig and of the boring itself, at thesame time, the outside diameter of the center-point sleeve 1 can be madeto considerable dimensions.

Also, the upper part of this principal body ends in a cone which allowsthe diameter of the center-point sleeve 1 to be made to fit that of theshaft-sleeve 2, and the cone also allows the center-point sleeve to beconnected to the shaft-sleeves by means of the intermediate flexiblehoop 3. According to the depths to be reached, this hoop can be ofdifferent design.

For slight depths, this hoop will be of the classic type and produced inreinforced rubber or in all other flexible materials which haveacceptable mechanical and chemical characteristics capable of resistingthe forces posed on it by the environment.

For medium depths, it is proposed to utilize a compressible bellows(FIG. 1a) in metal or in any other flexible material having acceptablemechanical and chemical characteristics and capable of resisting allforces imposed on it by the environment.

In an other variation of the embodiment, air cushions are also placed inthe undulations from the outside.

For great depths, a very strong ball and socket joint, (FIG. lb),capable of supporting the enormous vertical forces, is used thewaterproofing is insured by an assembly of inside joints 11. The forceapplied on the outside joint by the pressure of the water is balanced bya counter pressure applied to the inside surface. In the case of failureof an inside joint, the resulting flow is such that it can be held inspite of all the necessary pressure on the outside point, even beingable to be systematically created and recuperated to be put back intothe circuit.

The sleeve 4 (FIG. 3) of the shaft-rig consists of a steel sleeve 12 ofconsiderable thickness.

The sleeve 4 is intended for boring the hole in the implantation siteand, at the same time, to hold the entire installation in place.

This sleeve is connected to the body of the shaft-rig, by means of thecomplex deformable assembly 6 (FIG.

' 2 and 5) forming a supple joint which protects the fixed sleeveagainst all possibility of shock caused by shaft oscillations. Thisarticulation 6 (FIG. 2) is constituted by a membrane 13 in rubber or anyother flexible material, even metal, gripped between two sets of flangesand counter flanges, 14 and 15 as well as 16 and 17, forming awaterproof fitting.

The very great force, resulting from the outside water pressure, whichis exerted on this supple membrane 13 is balanced by a series ofhydraulic jacks 18 connected to one or several oleopneumaticaccumulators. Each jack 18 controls the movement of a section 19. Thetotal all of these sections 19 uniformly is distributed on the membrane13 thus making a stop bearing of multiple layers capable at all time toresist any collapse of the membrane 13.

In one variation of the embodiment, this articulation is obtained by aunit consisting of flexible joints 20 held in equilibrium by jacks 21also connected to an oleopneumatic compensator (FIG. 8).

During all rotational movement of the entire shafti'ig, intended forimplantation, it must necessarily be maintained rigid in order toeliminate all possibility of relative movement between the sleeve andthe entire body of the rig.

On the other hand, the membrane 13 must not be subjected to torsionforces in the perpendicular plane of its axis and to prevent suchforces, blocking parts 22 (FIG. 2) have been provided.

In an other variation of the embodiment, the joint 6 is obtained by aswivel similar to that described for the joint between the shaft sleeveand the center-point sleeve.

The sleeve 4 (FIG. 3) is very thick because of the enormous forces towhich it is to be subject, and especially because this wall is drilledlongitudinally with the channels 23 opening to the outside and intendedfor the injection of liquid concrete required to achieve the absoluteand sought waterproof condition.

This sleeve carries an external skirt at its upper part forming a crown24 which serves as a base its bell shape allowing the injected concreteto be held in position.

The sleeve ends at its lower part by a particular unit which forms thecrown drilling tool holder 25 needed for its implantation.

In the inside of the center-point sleeve 4 is placed the first drillingtube 5, the lower end of which preceded by the drilling head 26 carriedon the drilling shank 27, follows the progression of the center-pointsleeve 4 in driving.

In the annular space between the wall 12 of the center-point sleeve andthe drilling tube 5, are installed the conduit 28 for the injection ofwater under pressure and the conduit 29 for the extraction of drillingproducts.

The shaft-rig also comprises an implantation tool unit on the firstdrilling tube 5 (FIG. 6).

This tool has three functions which are: the blocking of the end of thecenter-point sleeve 4, the implantation of the first drilling tube 5,and the recuperation of the shaft-rig when the sleeve 4 and the firstdrilling tube 5 are implanted and the drilling work finished.

This tool comprises three cylindrical bodies 31, 32 and 33.

The first body 31 is arranged to allow the evacuation of drilling sludgeproduced by the sleeve 4 and the drilling head 26, at the same time.

The body is fixed by flanges and bolts on the same base as the shafts(FIG. 5). Two toric joints are provided on the double flange of cavity Bto ensure it is watertight.

This cavity B can be subjected to pressure so that it balances the forceof the water pressure on the toric point of the head.

In the interior of the body, in the cavity A, are installed the waterinjection conduit 28 and extraction conduit 29, as well as a purgeconduit 34 which allows the evacuation of the residue when thecenter-point sleeve has been implanted, the first injections of concretehaving been carried out, and the waterproofing has been ensured.

This purge conduit is also intended for the injection of the concreteinto the annular space between the tube 5 and the sleeve 4 when the tube5 has been implanted in its turn.

The first body 31 is surmounted by a suit intended for implantation ofthe first drilling tube 5.

This unit is composed of three essential parts:

a cylindrical frame 33 carrying the blocking handling clamps for tube 5,

the cylindrical body 32 which contains the tube 5,

and

an air chamber 35 is intended to feed air from cylinder 32. A drillingrod 27 passes through the unit and in case of leaks in the passages, thewater proofing is ensured by instantaneous static joints.

The first drilling tube 5 is housed in the body 32, it passes throughclamp 36 and descends to the center of the sleeve 4 to the base of thelatter (FIG. 3).

Air pressure on the piston 37 (FIG. 6) effects gradual driving of tube 5and the protection of the boring head 26.

This same piston 37 prevents all possibility of encroachment by waterand drilling sludge into cavity E.

The head of water which enters the cavities A and D, namely all thespace below the piston, is balanced by the air injected by pipe 38. v

A pneumatic pressure regulating device is connected to the conduit 39and allows constant high pressure to be maintained inside the unit andat the same time regulates the head of water within the limits imposedfor good progress of the boring operation.

The upper end of tube 5 is drilled with holes 40 intended for theevacuation of the drilling sludge and waste produced by the head 26.

Through the undermining work of the head of the sleeve 4, the tube 5 isheld in place and steadied by clamp 36 in a position such as shown (FIG.3) namely, slightly behind the base of the sleeve 4.

The drilling head 26 which is driven by a rotating table mounted abovethe tool unit inside the shafts, breaks down the central drilling-corecut out by the crown of tools 25 of the center-point sleeve 4.

The broken-down products are evacuated by the extraction pump whichsucks them out.

During the period of implantation by the centerpoint sleeve 4,practically no drilling sludge will pass into the inside of tube 5.

The level of the head of water is thus held at a minimum in order toallow an easier visual check on the workings through the port-holesprovided for this purpose.

When the pivot 4 is implanted, its crown 24 (FIG. 5) is in contact withthe bed, at least buried in the surface sands, and the rotation of theshafts is stopped.

The injection of concrete into the outside of the sleeve 4 is thencarried out by means of the holes 23 provided for this purpose.

These first injections are limited to the lateral part of thecenterpoint sleeve and. particularly in the upper part (on averagetwo-thirds from the top) and under the support flange.

In this first stage concrete is not injected into the base of the sleevesince it would prematurely flow into the interior, itself, of the sleeve4. 7

When the first injections are finished and the concrete has set, theboring head 26 carries on the work. As the tube 5 progresses, it goesdown into the drilling under the action of the thrust from compressedair fed on to the piston 37.

When the tube 5 is in place, the drilling head 26 is drawn up againunder the piston 37.

With the aid of the purge conduit 34 and the extraction pump, theannular cavity between the tube 5 and the sleeve 4 is cleared of thesludge therein.

In the annular space the level is held below the lower diaphragm 30. Theconcrete plug is poured in the annular space limited by the twodiaphragms 30, then for a last time, the residual mud accumulated at thebase of the sleeve is evacuated.

As this moment, by conduits opening into the base of the center-pointsleeve a large quantity of concrete is injected. In case of particularlysoft terrain, concrete can be also injected by the purge conduit 34.

When all work has been finished, the shaft-rig is implanted'and held inplace by the center-point sleeve.

The preparatory work to the boring operation is finished.

In terrain which is particularly soft the first boring tube 5 can beprolonged as required. But before all dismantling of the assembly ofcylinder 32 allowing the boring to proceed, a very close check ofexterior waterproofing of sleeve 4 must be carried out in order to avoidall possibility of the shafts being inundated a state which is no longerguaranteed by the cap unit on the head of the center-point sleeve.

For the implantation of the shaft-rig itself, the work can be carriedout with the help of the floating workshop (FIG. 10).

The floating workshop is essentially intended for the the transport ofmaterial, for assembly and implantation of the shaft-rig on site, and isaccordingly equipped.

This equipment fundamentally consists of a very powerful revolving table41, jointed in all azimuths, and with a gantry hoist 42, especiallydesigned for handling and positioning components on the axis of thetable 4 l.

The rotating table 41 is intended to drive units of shafting duringimplantation of the center-point sleeve The fore end of the workshopvessel has a normal stem with a classic hull shape up to the beam. Thestem half consists of two distinct hulls 43, separated by an open spacehaving a V-shape (FIG. 10).

The space between these two hulls 43 forms a calmbelt and in this calmspace the mounting and the implanting work of the shaft-rig are carriedout.

The rotating table is mounted on four columns 44, two of which are oneach of the two hulls 43 of the vessels.

These columns 44 are both supports and guides for the vertical movementof the unit.

This vertical movement is ensured by jacks centered in the columns 44. I

The two beams 45 (FIG. 12) allow longitudina movement. I

All the articulations are mounted on central rollers in order toeliminate all possibility of seizing and jamming.

The vertical axle of the table 41 passes through the center of gravity Gof the vessel.

The introduction and the placing of the sleeves in the diagonallytrussed well 41 is ensured by the gantry bridge 42 which is moved onroller tracks 47 in order to serve all the forward area of the vesselwhere the shaftrig sleeves are stored.

The gantry bridge 42 and its operating cabin are of special design. Thelongitudinal and transversal translation are effected by two sprocketand chain units which allow all handling in a calm or rough sea.

In a variation of the embodiment, the implantation of the shaft-rigs iscarried out by self-propulsion rotationally of the center-point sleeve,owing to two pairs of motor-driven propellers mounted on the base of theshafts (FIG. 1).

In this case, the rotating table 41 no longer serves as a guide for theshaft casings. The mechanism is very simplified since in this solution,the centering sleeve of the rotating table is provided with centeringrollers on which the sleeves of the shaft-rig rests and rolls.

In another variation of the embodiment of the implantation ofshaft-rigs, the center-point sleeve 4 is driven in rotation by the meansof a worm drive 49 and 50 (FIG. 8), thus producing a self-drillingshaft-rig. These last two types of implantation are particularlyrecommended in the case of medium and very great depths.

The general arrangement of self-drilling rigs are similar to those ofthe two first embodiments, given the need to balance the couple createdby the gear and worm screw unit on the outside of the base of the rigs,the center-point sleeve must be stabilized by brakes. These brakesconsist of two diametrically opposed paddles installed in such a waythat they can be worked as required, from inside the shafts.

In this solution the entire tooling, intended both for recuperation ofsludge and for the positioning of the first drilling tubes, isnecessarily mobile in relation to the sleeve of the shafts which isfixed. The evacuation of sludge and all other products must thus be madefirst in this tooling and, next, the rotation of the centerpoint sleeve4 is stopped and the drilling products accumulated in this space, areevacuated to the outside joining the part to be emptied with theevacuation orifice, provided with this in view, in the sleeve of theshaft-rig, by a hoop, the inlet and outlet being blocked by the workingvalves.

These three types of shaft-rigs have one point in common. Their whole isone sleeve which emerges on the surface. On the platform which caps thisend, the classic drilling derrick can be positioned.

This solution can be retained in the case of slight depths, as thelength of the jointed rods from the surface to the attack on theunderwater bed are not prohibitive.

In the case of medium and very great depths, it is preferable to utilizea jacked bridge (FIG. 4) installed inside the shafts.

The design of this handling gear allows the need for the libe ration ofthe center of the shafts to be omitted.

Similarly, the rotating table installed inside the shafts is conceivedin such a way that it can also be omitted or put into the position forworking in at least two different stages, on the one hand, above thetooling when implanting the center-point sleeve 4, and, on the otherhand, a little nearer the head of sleeve 4, when the tooling isdismantled and replaced by that intended for the boring.

The placing of the jacked bridge can follow variations in gradient.

On the other hand, when the workshop vessel has carried out its work onthe shaft rigs, it must be freed to carry out other implantations asthis is an extremely costly unit and, therefore, its immobilization mustbe very short. Also, it is anticipated to replace this workshop shipwith a pontoon workshop (FIG. 13).

The workshop pontoon is equipped with all necessary gear for drillingand machines intended to feed the shafts by motive force (electricity,compressed air and hydraulic energy), it is provided with all kinds ofrequired installations for the comfortable lodging of crews and drillingteams.

This pontoon would take the place of a workshop vessel. It must, as aunit in itself, support the sleeved shaft. Thus, its emerging part mustbe girdled with an articulated unit 51in all azimuths, as the ship, butin which the driving of the shafts will be replaced by a simple sleevewith central rollers 52. This sleeve and its outside support would be intwo parts, joined by bolts in such a way as to be able to be mounted onthe shaft sleeve of the shaft-rig by its traverse.

The vertical movement due to the tides and swells will be made directlyon the sleeve of the shaft-rigs which serve the roller track by thecentral rollers 52.

The pontoon is equipped with windlasses, fore and aft, handling winchesand the necessary capstans for all operations at the same time, whenbeing put into place and during all drilling work.

The end and side propellers 53 allow a stabilization of the whole unitand help to maintain the axis substantially in the center of gravity. Italso permits the vessels head to be held on to the swell.

As shown (FIG. 13 and 13a) this pontoon is in two jointed parts andflexibly held together by hinged joints.

When the collar of the shafts is engaged in the space reserved for it,the aft part of the pontoon swings about the axis 54 and closes andlocks itself in the devices provided with this in view.

The transport, mooring and the lifting of anchors intended for stayingthe shaft-rigs is a very important work. Also in order to complete thisinstallation, it is necessary to produce a tumbler (FIG. 14 and 9).

The tumbler is a small boat specially designed and equipped for thetransport, the casting, and weighing of anchors and buoys intended forstaying shafts. It also allows the carrying out of the mooring of thesebuoys to shafts.

The tumbler is fundamentally composed of a hull consisting of twocaissons 55, joined together by a series of cradles 56. Each cradle 56supports a group consisting of one buoy and one kentledge 57.

The whole is straddled by a toric bridge 58, which moves on tworoller-tracks 59. This movement is carried out by casings, each end ofwhich is provided with a brake 60 which allows an absolute blocking intoplace of the gantry bridge.

The movement of the bridge is ensuredby a winch 61, and the chain andsprocket assemblies 62, 63 and 64.

Each of these roller-tracks is provided with two or four mobileintermediary supports which are intended to support to the nearestextremities of the roller housings 66, the tube, in order to ease theefforts due to lifting a kentledge 57. These intermediary rests areblocked, as required, as is the deck of the vessel.

The gantry bridge is provided with such supports. These are arranged onthe lower part of each housing 66 coming into contact with the pointsforeseen on the deck.

The entire frame work of the gantry contains the winches intended tohandle the mooring and the weighing of kentledges and buoys.

The shafts of chains are arranged in each of the caissons which form thehull of the vessel.

Such an installation allows the implantation of underwater recuperablebases intended for the extraction of petroleum and gas or any otherproducts accumulated in the soil itself, or on the surface of the seabed, by means of shaft-rigs open to the air.

These same shaft-rigs can be employed for the implantation of basesintended for the anchoring of support pylons, floating or fixed islandsor all other maritime surface installations.

These shaft-rigs allow drilling crews to work at the bottom of the shafthead under conditions identical or similar to those encountered duringland drillings. In fact, the work at the bottom is carried out in theopen air, namely in all circumstances at atmospheric pressure.

When the drilling is finished, three hypotheses can be demonstrated: thedrilling is unproductive (no product or non profitable products), thedrilling permits a profitable exploitation where the shafts remain inplace for the duration of the exploitation of the drilling. In the casewhere the drilling is unproductive, it is indispensable to immediatelyrecuperate the whole of the installation apart from the center-pointsleeve 4 which is implanted for good in the sea bed.

All the tools intended for drilling are dismantled. The head of thesleeve 1 is stripped of all accessories. It is then capped with acylindrical chamber or a nosecap" which is connected to the base of theshaft-rig by a flange. This nose-cap carries a tool essentiallyconsisting of a set of keys 68 which, passing through a stuffing-box andbalanced by compression springs, mounted on bearings, can be operatedfrom inside the shaft-rig.

These keys are intended to undo the bolts 69 which join the shafts tothe center-point sleeve by means of flanges.

In order to carry out this dismantling operation, the water ballasttanks are filled up and, consequently, allow pressure to be transferredfrom one flange to the other.

When the screws are taken out, the water rushes into the cavity and thehead of the sleeve. The force thus produced by the water on this freesurface cooperates with the give of the water ballast to slacken off thebase of the shaft from the head of the center-point sleeve.

Owing to the give provided by the water ballast, the shaft-rig isbrought up again, sleeve by sleeve, and recuperated on the workshopvessel.

Re-equipped with a new center-point sleeve, it can them be put back intoservice again.

In the second case, where the drilling allows a profitable exploitation,the head of the center-point sleeve 4 is blocked up by a base plate 70.On this base plate 70 is placed the drilling material and all itsaccessories. This unit is then held within a hermetic space consistingof a cylindrical chamber 71 closed by a cover provided with a valve andconnected to the head of the center-point sleeve by studs.

The cover is provided with a valve and a manhole 73.

The joints of the elements constituting the drilling material is madethrough the wall of the body 71 and the blocking off is ensured by thevalves which can be remote-controlled.

The whole of the chamber 71 and of its cover 72 is capped in its turn bya second cylindrical chamber 67 connected to the bottom of the shafts,as indicated in the preceding case, which allows recuperation in thiscase.

In the second hypothesis, it would be necessary to periodically visitthe drilling material. Thus a nacelle 74, consisting of a unit, isforeseen: living space, water ballast tanks, such machinery to becapable of, at all times, being brought into equilibrium inside itself,with the environment in which it is found.

A living chamber 75, specially arranged, allows several men to livethere at normal atmospheric pressure for several hours or several days.

This nacelle which can be guided by remote control or connected to thesurface by means of a cable, or be independent and piloted by itsoccupants, sits on top of the chamber 71 fitting to its cover 72 bycentering on the studs and on the rim with the help of the volume in thewater ballast tanks 76.

A device of special nuts and studs allow it to be hermetically fixed onthe head of the shaft.

An air purge cleats water from cavities 77 and 78 at the same time.

When the nacelle is in place and the waterproof state has been verified,the plugs 79 and 73 are lifted out to give access to the drillingmaterial.

When work is carried out, the plugs are replaced and the nacelle freedto rise back to the surface.

For particular reasons of exploitation, it can be used to maintain thewhole shafts rig in place during the whole duration of the exploitationof the drilling which is carried out according to the third caseenvisaged above.

This method allows an easy access to the head of the shafts which remainin the open air.

In this case, the workshop ship must be freed and replaced by theworkshop pontoon, foreseen with this in view.

When the exploitation is finished, it will be necessary to recuperatethe shaft-rig. This operation can be performed according to the pro cessin the first case.

It is obvious that the invention is not limited by the example describedand illustrated above, from which can be anticipated other forms andother methods of the embodiment without departing from the scope of thepresent invention.

What is claimed is:

1. Installation for laying an underwater, recoverable base forextracting by means of drilling means oil, gas or any other usefulproducts available under the sea bed, by anchoring supporting masts,floating or fixed islands, or other surface offshore installations,which comprise: a recoverable well having means opening into the freeatmosphere and having transverse dimensions sufficient to enable a gangof workmen to have access to the bottom of said well; drilling means forperforming a drilling operation installed in the bottom of said well; awell base pivot permanently sinkable in the sea bottom bed; means forrotatably driving said base pivot about its longitudinal axis in orderto sink same into the sea bed; and water-tight flexible connecting meansdisposed between said base pivot and said well to allow a slightinclination or oscillation of said well in relation to said base pivot.

2. Installation as set forth in claim 1, wherein said water-tightflexible connecting means disposed between said base pivot and said wellcomprises a flexible membrane, a set of flanges one carried by said welland the other by said base pivot for gripping the edges of saidmembrane, and a presser cylinder and piston units positioned to exert apressure on the membrane portion lying inside said well and to reactagainst a fixed point on said base pivot to balance the externalpressure.

3. Installation as set forth in claim 1, wherein said means forrotatably driving said base pivot comprises propeller power units havinghorizontal axes and disposed externally and at spaced intervals aboutthe periphery of said well.

4. Installation as set forth in claim 1, wherein said well comprises atits lower end a working chamber at atmospheric pressure and adouble-walled body constituting a fluid-tight annular jacket receptiveof a ballast material for compensating the Archimedean thrust.

5. Installation as set forth in claim 1, wherein said base pivotcomprises a cylindrical body having a relatively thick wall, meansdefining channels extending longitudinally in said wall opening at oneend into said body and at the other end to the outside of said body topermit the injection of concrete, a retaining bell for preventing theinjected concrete from rising, a first drilling tube housed within saidbase pivot, a drilling rod and head unit housed in said first drillingtube, and at least one tube for injecting water under pressure andevacuating the drilling products disposed in the annular space bound anddefined by the cylindrical body of said base pivot and said internaldrilling tube.

6. Installation as set forth in claim 1, including at least a lowerpivot pipe and an upper well pipe, and mechanical means assembling saidpipes in an end to end relationship while allowing a slight oscillationof one pipe in relation to the other.

7. Installation as set forth in claim 6, wherein said mechanical meanscomprises a compressible bellows.

8. Installation as set forth in claim 6, wherein said mechanical meanscomprises a ball-joint, and sealing elements fitted in said ball-joint.

9. A partly reusable installation for extracting products from a sea bedcomprising: a reusable well section having an elongated, hollowconfiguration and having sufiicient interior transverse dimensions toenable workmen to pass through said well section from one end to theother end and positionable in a vertical disposition in the sea tocommunicate said one end with the atmosphere whereby the interior ofsaid well section is at atmospheric pressure during use of theinstallation; a well base section having anchoring means responsive torotation thereof for permanently anchoring said well base section in thesea bed; water-tight flexible connecting means releasably and flexiblyconnecting together said reusable well section and said well basesection to enable relative movement therebetween; extracting apparatusdisposed within said reusable well section at said other end thereof andextendable through said well base section into the sea bed to extractproducts from the sea bed; and drive means for rotationally driving saidanchoring means to effect permanent anchorage of said well base sectionin the sea bed.

10. An installation according to claim 9; wherein said water-tightflexible connecting means includes means connecting said reusable wellsection and said well base section together for rotation as an integralunit; and wherein said drive means comprises a plurality of ro ellersconnected in circu ere tiall s ac d-a art i elafionship around the exterib r o said riisa ble vell section for effecting rotation thereof.

1. Installation for laying an underwater, recoverable base forextracting by means of drilling means oil, gas or any other usefulproducts available under the sea bed, by anchoring supporting masts,floating or fixed islands, or other surface offshore installations,which comprise: a recoverable well having means opening into the freeatmosphere and having transverse dimensions sufficient to enable a gangof workmen to have access to the bottom of said well; drilling means forperforming a drilling operation installed in the bottom of said well; awell base pivot permanently sinkable in the sea bottom bed; means forrotatably driving said base pivot about its longitudinal axis in orderto sink same into the sea bed; and water-tight flexible connecting meansdisposed between said base pivot and said well to allow a slightinclination or oscillation of said well in relation to said base pivot.2. Installation as set forth in claim 1, wherein said water-tightflexible connecting means disposed between said base pivot and said wellcomprises a flexible membrane, a set of flanges one carried by said welland the other by said base pivot for gripping the edges of saidmembrane, and a presser cylinder and piston units positioned to exert apressure on the membrane portion lying inside said well and to reactagainst a fixed point on said base pivot to balance the externalpressure.
 3. Installation as set forth in claim 1, wherein said meansfor rotatably driving said base pivot comprises propeller power unitshaving horizontal axes and disposed externally and at spaced intervalsabout the periphery of said well.
 4. Installation as set forth in claim1, wherein said well comprises at its lower end a working chamber atatmospheric pressure and a double-walled body constituting a fluid-tightannular jacket receptive of a ballast material for compensating theArchimedean thrust.
 5. Installation as set forth in claim 1, whereinsaid base pivot comprises a cylindrical body having a relatively thickwall, means defining channels extending longitudinally in said wallopening at one end into said body and at the other end to the outside ofsaid body to permit the injection of concrete, a retaining bell forpreventing the injected concrete from rising, a first drilling tubehoused within said base pivot, a drilling rod and head unit housed insaid first drilling tube, and at least one tube for injecting waterunder pressure and evacuating the drilling products disposed in theannular space bound and defined by the cylindrical body of said basepivot and said internal drilling tube.
 6. Installation as set forth inclaim 1, including at least a lower pivot pipe and an upper well pipe,and mechanical means assembling said pipes in an end to end relationshipwhile allowing a slight oscillation of one pipe in relation to theother.
 7. Installation as set forth in claim 6, wherein said mechanicalmeans comprises a compressible bellows.
 8. Installation as set forth inclaim 6, wherein said mechanical means comprises a ball-joint, andsealing elements fitted in said ball-joint.
 9. A partly reusableinstallation for extracting products from a sea bed comprising: areusable well section having an elongated, hollow configuration andhaving sufficient interior transverse dimensions to enable workmen topass through said well section from one end to the other end andpositionable in a vertical disposition in the sea to communicate saidone end with the atmosphere whereby the interior of said well section isat atmospheric pressure during use of the installation; a well basesection having anchoring means responsive to rotation thereof forpermanently anchoring said well base section in the sea bed; water-tightflexible connecting means releasably and flexibly connecting togethersaid reusable well section and said well base section to enable relativemovement therebetween; extracting apparatus disposed within saidreusable well section at said other end thereof and extendable throughsaid well base section into the sea bed to extract products from the seabed; and drive means for rotationally driving said anchoring means toeffect permanent anchorage of said well base section in the sea bed. 10.An installation according to claim 9; wherein said water-tight flexibleconnecting means includes means connecting said reusable well sectionand said well base section together for rotation as an integral unit;and wherein said drive means comprises a plurality of propellersconnected in circumferentially spaced-apart relationship around theexterior of said reusable well section for effecting rotation thereof.